Process for cracking hydrocarbon oils



Jan. 31, 1933. J. G. AL'rHER PROCESS FOR CRACKING HYDROCARBON OILS FiledAug. 23.

Patented Jan. 31, 1933 UNITED STATES PATENT OFFICE JOSEPH G. ALTHER, OFCHICAGO, ILLINOIS, ASSIGNORTD UNIVERSAL OIL PRODUCTS COMPANY, OFCHICAGO, ILLINOIS, A CORPORATION OF SOUTH DAKOTA PROCESS FOR CRACKINGHYDROCARBON OILS Application led August 23, 1926. Serial No. 131,025.

This invention contemplates the provision of an improved process for theconversion of high boiling point hydrocarbon oils into hydrocarbon oilsof lower boiling point and itis a specific object of the invention toprovide a process for the continuous conversion of hydrocarbon oils witha minimum of coke formation.

One of the great diiculties which has materially reduced `,theeiiiciency of cracking processes has been the excessive formation ofcarbon during the cracking reaction. There have been various attemptsmade yto develop efficient cracking processes, many of which arecommercially successful, but in these processes provision has been madefor taking care of excessive accumulations of coke rather than for theVreduction of coke formation during the cracking reaction. It has beenalmost universally the custom in what are known as lcontinuous processesto provide an enlarged chamber in which the carbon and coke likeaccumulations resulting from the reaction of the oil collect. My processspecifically contemplates an improvement in a continuous process of thisgeneral character. In such processes the accumulations of so-called cokecontain a high percentage of oils which it is desirable to recover.Various methods have been devised for treating the coke like residue'from a cracking process but these methods are directed to the treatmentof the residue subsequentIto the cracking operation. My inventioncontemplates the treatment of the coke like residue as a step in thecontinuous cracking process. I have found that substantial quantities ofthe materials other than carbon contained in the coke like residue canbe dissolved therefrom by the employment of a. suitable solvent oil.Accordingly in my process I introduce into the accumulating mass of cokelike residue quantities of reiux condensate separated from the vapors inthe cracking process,'such reflux condensate functioning as a solventoil for dissolving the materials other than carbon in the coke likeresidue.

My invention will be more clearly understood from the followingdescription which,

of the charging oil can be passed through the line 7 and conveyedthrough the closed conduit 9 in heat interchange relation with vaporsundergoing dephlegmation in the primary dephlegmator D, the oil thenceflowing through the line 10 to the heating coil A. The charging oil isgiven its cracking heat While flowing through the heating coil A and isthence delivered by Way of the line 11 controlled by the valve 12 to thereactionL and mixing chamber B. 'It is to be noted that no vapors .aretaken off from the reaction and mixing chamber B for dephelgmation. Theoil is adapted to pass from the chamber B through any one of the lines13 controlled by the valves 14 into the separating chamber C. Thevaporized constituents of the oil leave the chamber C through the line15 controlled by the valve 16 and are conveyed to the primarydephlegmator D wherein portions of the insuliiciently cracked vapors arecondensed forming reflux condensate. The vapors uncondensed in theprimary dephlegmator D pass to the secondary dephlegmatorE through theline 17 controlled by the valve 18. It is to be understood that theseveral valves l2, 13, 16 and 18 may all be employed for the purpose ofregulating the pressure conditions maintained in the several elements ofthe apparatus.l The dephlegmated vapors issuing from the secondarydephlegmator E pass through the line 19 controlled by the valve 20 to asuitable condenser F from which the condensatellows throughV the line 21controlled by the valve 22 into the receiver G which is 4of conventionalform being provided with the valve controlled distillate draw-olf line23 and like'residue. Accordingly I return this re- -the refluxcondensate separated from the lvapors in. thedephlegmator D may bereturned through the line 25, valve 26, pump 27 and valve`28 to the rawoil charging line 3. or by suitably regulating the valves 26, 28 and 29.This refiux condensate may b`e permitted to flow by gravity through thebypass vv30 into the charging line 3 to be fed 'with the charging oilthrough the heating coil for further cracking.-

The less refractory reflux condensate collecting in the dephlegmator Dconstitutes a very good solvent oil for treating the coke fluxcondensate from the dephlegmator D through the line 31, valve 32, pump33, valve 34 and line 37 into the reaction and mixing chamber B, whereinthe coke like residue accumulates, through any one of the lines 38controlled by the valves 39 depending upon the uantity of material inthe chamber B. The y-pass on the line 36 in which is positioned a valve35 is provided for by-passing the pump 33. In order that the refluxcondensate returned to the body of material in the reaction chamber Bwill not retard cracking by lowering the temperature of materialtherein, I- provide for heating the reflux condensate from thedephlegmator D prior to its introduction to the chamber B. To this end aline 43 controlled by a valve 42 communicates with the line 37 and maybe employed for conveying the reflux condensate to the reflux heatingcoil H positioned in the cracking'furnaoe from which the heated refluxcondensate is conveyed through the line 44 controlled by the valve 41back to the yline 37. It is to be noted that by suitably controlling thevalves 40, 41 and42 the reflux condensate can be either passed throughthe heating coil H or introduced directly into the chamber B.

The hot relux condensate introduced to the chamber B functions todissolve substantial quantities'of thecoke like precipitate colleeted inthis chamberand the dissolved constituent/s of the oil together with thereflux condensate pass to the separating chamber C leaving only a smallvolume of a substantially carbon'like residue in the chamber B.Substantial vaporization takes place in thek chamber C and vapors aretaken off from this chamber for dephlegmation, as above described. Theunvaporized oil collecting in the chamber C is of a very differentcharacter than the liquid residue accumulating in the reaction zone ofthe usual continuous cracking process in that' it contains substantiallyno carbon. This residue can therefore` be successfully retreated in theheating zone of @5 the cracking process. I therefore provide for fromthe vapors to the oil passing drawingof unvaporized oil from the chamberC through any one of the lines 45 controlled by the valves 46, and thisunvaporized oil may be returned to the heating coil by way of the line47, pump 48, and valves 49 and 50. In some operations or inthe treatmentof exceedingly refractory oils it may not be desirable to return thisoil to the heating zone in which event the same can be passed to anyvsuitable storage through the line 51 controlled by the valve 52.

The process is exceedingly flexible and capable of variousmodifications. I have, however, found that good results can 'be obtainedprimary dephlegmator D at a temperaturev of substantially 550 F. whiletaking oE/only end point gasoline, i. e. 437 F. from the top of thesecondary dephlegmator E, and during the operation maintaining a uniformpressure of substantially 135 pounds per square inch. It must beappreciated that I do not limit myself to these particular conditions ofoperation since they may vary widely in the treatment of various oils.It furthermore may be advantageous to maintain lower pressures on thedephlegmators than is maintained inthe heating coil A and fr chambers Band C. It may also be desirable in some operations to lower the pressurein the chamber C somewhat lower than the pres-l sure maintained in thechamber B. By properly controlling the various lvalves shown suchconditions can be maintained.

Since the rate of coke formation is largely dependent upon' the oiltreated,I no specific data is here given as tothe quantity of coke.

formation. It has, however, been found that by employing a solvent oilin-treating the coke like residue in the processV the coke productioncan be lowered to form 1/2 to 1,41

the normal production. From the foregoing it will be seen that myprocess contem lates the inclusion vin the continuous crac ing processof steps which materially reduce the coke formation and which therebyincrease the efliciency of the cracking process.

Having thus described my invention, what I claim is:

1. A process 60xcracking hydrocarbon oil comprising initially subjectingthe oil to a crac ing temperature, thence passing the oil through areaction zone wherein a time period of reaction is allowed withoutincrease in temperature of the oil, in passing the oil from the reactionzone to a separating chamber maintained under a lower pressure than thepressure in the reaction zone, takingof vapors from said separatingchamber, subjecting such vapors to reiux condensation and in returningreflux condensate se aratel the reaction chamber without previouslycommingling with the oil being treated in the process, controlling thetemperature of the reflux condensate returned to the oil in the reactionzone by separately heating predetermined portions of the returned refluxcondensate prior to introduction thereof to the reaction zone.

2. A process for converting high boiling point hydrocarbon oils intolower boiling point hydrocarbons comprising initially subjecting the oilto a cracking temperature,v

thereafter maintaining the oil under cracking conditions in a reactionzone, passing the oil from the reaction zone to a separating zonemaintained under a lower pressure than the pressure in said reactionzone Wherein substantial vaporization occurs, subjecting the vapors toreiux condensation, uniting the less refractory portion of the refluxcondensate with the oil in said reaction zone, and controlling thetemperature of the reflux condensate returned to the oil in the reactionzone by separately heating predetermined portions of the returned refluxcondensate prior to introduction thereof to the reaction zone.

3. A hydrocarbon oil cracking process which comprises subjecting the oilto cracking conditions of temperature and pressure While passing thru aheating zone, discharging the heated oil into a reaction zone maintainedunder conversion conditions and effecting a separation of vapors fromunvaporized oil, subjecting the separated vapors to primary andsecondary dephlegmation, introducing charging oil for the process intodirect contact with the vapors undergoing secondary dephlegmation,passing another portion of charging oil for the process in indirectlieat exchange relation with the vapors undergoing primarydephlegmation, passing the commingled chargin oil'and reiux condensatefrom the secondary dephlegmation to said heating zone to be subjected tocracking conditions of temperature and pressure therein, independentlyheating reflux condensate produced by said primary dephlegmation andintroducing the sametosaid reaction zone, and condensing the vaporsuncondensed by said secondary dephlegmation.

JOSEPH G. ALTHER.

